First, simply invoking the Laffer curve is irrelevant. I think most of us implicitly understand that there is a maximum revenue somewhere above 0% and below 100

First, simply invoking the Laffer curve is irrelevant. I think most of us implicitly understand that there is a maximum revenue somewhere above 0% and below 100% taxation. What's not obvious is where that is, ie whether current tax rates put us above or below maximum revenue. Second, people will always avoid tax, period. If one can spend $1 to save $10, then people will, no matter how low the tax rate is. The bare existence of tax avoidance is not a sufficient indication that the tax rate is too high. Third, no one wants the "taxman" to lose money trying to reclaim taxes. There are obviously more options than the two you are strawmanning: A) lose money trying to reclaim taxes and B) lower the tax rate.